[RFC PATCH 1/2] mm/huge_memory: check split_underused_thp in the caller of deferred_split_folio()

["Jose A. Perez de Azpillaga" <azpijr@gmail.com>]

deferred_split_folio() ignores folios that aren't partially mapped when
shrink_underused is off. map_anon_folio_pmd_nopf() is the only caller
that always passes false, so move the check there. The next patch queues
folios without PG_partially_mapped for another reason.

migrate_folio_move() passes false when the source was queued without the
flag, and now requeues the destination even if shrink_underused was
turned off in the meantime.

Signed-off-by: Jose A. Perez de Azpillaga <azpijr@gmail.com>
---
 mm/huge_memory.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 0d589be136d2..8c4a69c797ed 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1403,7 +1403,8 @@ void map_anon_folio_pmd_nopf(struct folio *folio, pmd_t *pmd,
 	folio_add_lru_vma(folio, vma);
 	set_pmd_at(vma->vm_mm, haddr, pmd, entry);
 	update_mmu_cache_pmd(vma, haddr, pmd);
-	deferred_split_folio(folio, false);
+	if (split_underused_thp)
+		deferred_split_folio(folio, false);
 }
 
 static void map_anon_folio_pmd_pf(struct folio *folio, pmd_t *pmd,
@@ -4631,9 +4632,6 @@ void deferred_split_folio(struct folio *folio, bool partially_mapped)
 	if (folio_order(folio) <= 1)
 		return;
 
-	if (!partially_mapped && !split_underused_thp)
-		return;
-
 	/*
 	 * Exclude swapcache: originally to avoid a corrupt deferred split
 	 * queue. Nowadays that is fully prevented by __memcg1_swapout();
-- 
2.56.0